1. Field of the Invention
The present invention relates to a method for manufacturing an organic light-emitting device.
2. Description of the Related Art
A multicolor organic light-emitting device is a light emitting device made by combining a plurality of organic light-emitting elements having different emission colors. Here when the multicolor organic light-emitting device is manufactured, it is necessary to selectively form a plurality of light-emitting layers having different emission colors in a predetermined region. Various methods have been used in order to selectively form the light-emitting layer emitting such a predetermined color in the predetermined region, and a method of patterning the light-emitting layers using a photolithographic method is available as one of such methods.
In Japanese Patent No. 3839276, a method has been proposed in which an organic compound layer is dry-etched to partially remove the organic compound layer to be unnecessary when the organic compound layer containing a light-emitting layer is patterned using the photolithographic method.
Specifically first, a film of a first organic compound layer is formed entirely on a substrate on which a first pixel electrode and a second pixel electrode have been formed in pattern. Subsequently, a portion where the first organic compound layer is formed is provided with a resist later that covers the first organic compound layer using the photolithographic method, and the first organic compound layer in a region not covered with the resist layer is selectively removed by dry etching. Subsequently, a film of a second organic compound layer is formed entirely, a portion where the first organic compound layer and the second organic compound layer are formed is provided with a resist layer by the photolithographic method, and the second organic compound layer in a region not covered with the resist layer is removed. Finally, layers formed on the resist layers are stripped using a resist stripper, and a common electrode is formed on the patterned first and second organic compound layers. By the above method, a light-emitting device provided with the plurality of organic light-emitting elements by patterning the plurality of organic compound layers is formed.
When the organic compound layer is patterned according to the method discussed in Japanese Patent No. 3839276, a substrate provided with a transistor (Tr) and a wiring layer for driving the organic light-emitting element is used in some cases. In such a case, before forming the pixel electrode and the like, it is necessary to form an organic planarizing layer that covers Tr and the wiring layer in order to smoothen and planarize roughness due to Tr and the wiring layer. If necessary in some cases, an organic pixel separation film that covers edges of the pixel electrode is formed on the organic planarizing film for the purpose of smoothening an unevenness produced depending on the film thickness of the pixel electrode as well as laying out a light-emitting region of each light-emitting element.
The organic planarizing film and the organic pixel separation film are members composed of the same organic material as in the organic compound layer. When the layer is patterned by the method discussed in Japanese Patent No. 3839276, the inconvenience described below may occur under a circumstance where the member composed of the organic material is exposed on a surface of the substrate.
A time period when dry etching is performed is adjusted not to leave a film of the organic compound layer on the electrode provided in the region where the dry etching is performed. Specifically, the time period required for removing the organic compound layer is calculated from the film thickness of the organic compound layer and an etching rate of the organic compound layer. The dry etching is performed for a longer time than the time period required for removing the organic compound layer.
The etching rate of the organic planarizing layer and the organic pixel separation layer is almost the same as the etching rate of the organic compound layer. Thus, after removing the organic compound layer by the etching, the organic planarizing layer and the organic pixel separation layer arranged between the first and second pixel electrodes and in a circumference of a display region are also etched similarly to the first organic compound layer. As a result, depressions occur in the organic planarizing layer and the organic pixel separation film provided in the region exposed to the etching, and an excessive unevenness occurs between the first organic compound layer and the organic planarizing layer or between the first organic compound layer and the pixel separation film. If this is the case, when the second organic compound layer or the film of the common electrode is formed, the second organic compound layer or the common electrode is sometimes partially broken or thinned due to this excessive unevenness. The broken part and the thinned part of the second organic compound layer and the common electrode cause a short circuit between the electrodes of the organic light-emitting elements and become a resistance in a current supply circuit to cause impaired properties in the organic light-emitting device.
In Japanese Patent No. 3839276, the substrate is washed with water after developing the resist layer in a step of patterning the organic compound layer using the photolithographic method. At that time, if the member composed of the organic material is exposed on the surface of the substrate, the water penetrates and is absorbed/stored in the organic planarizing layer and the organic pixel separation film. Thus, it takes a long time to dehydrate the member, and the residual water is leaked at the time of use of the light-emitting device to reduce the properties of the organic light-emitting element.